I have experience with both. The 6.7 Ford isn't doing too bad as far as issues, but it's also a newer motor on the market. I would not recommend a Ford 6.0 or 6.4L at all. As far as the Cummins, they're great motors. We don't see a lot of issues with them. Another option is to find an old Ford 7.3L, those things are great motors and trucks hold their value.
My buddy has a 2015 6.7 platinum which is beautiful and very quick. Im not afraid of an 05-07 6.0 as I can get it bullet proofed to take care of its issues. I dont want an old 7.3, mostly due to the fact that its old technology (front leaf springs, old interior), I want something as new or newer than the jeep (2007). Ive heard some issues with the the turbos on the early ford 6.7s but that can be fixed. It will come down to my budget and a few test drives when the time comes
I wouldn't touch a 6.0L myself.
Looks like something off of Mad Max.
Which makes it awesome.